Collars are available as chokes or martingales in Kangaroo, and Paracord. Kangaroo Leather collars come braided around a nylon core to help prevent stretching. When measuring for collars measure around the dogs neck where you wish the collar to settle. Add at least one inch to this measurement to allow collar to slip over the dogs head. Choke collars are also available with a snap and lose ring for dogs whose head is bigger around then their neck. For martingale collars measure around neck and decide if you want the collar to "tighten" beyond this point.